Sodium nitrate and tungsten as matrix modifiers for the determination of arsenic in shotgun pellets by electrothermal atomic absorption spectrometry

A method for the determination of arsenic in a complicated sample matrix by Zeeman effect electrothermal atomic absorption spectrometry using tungsten and sodium nitrate as matrix modifiers was developed. The determination of arsenic in SRM C2416 (Bullet Lead) and SRM 2710 (Montana Soil) by ETAAS us ing a mixture of palladium and magnesium nitrate as a matrix modifier faile d to obtain the certified concentrations at the 95% level of confidence usi ng the t-test. Both tungsten and sodium nitrate as matrix modifiers stabili zed arsenic so that the certified concentrations of the SRMs were determine d with high accuracy and precision (RSD < 4%). The high values of the regre ssion correlation coefficients (r > 0.999), with low detection and quantifi cation limits, were obtained in the calibration range 20-100 mug L-1. Sampl e matrix interferences can be eliminated by increasing the pyrolysis temper ature to 1400 degreesC with tungsten and to 1500 degreesC with sodium nitra te matrix modification. The standard additions method was also carried out in the case of SRM C2416 in order to check the linear relationship between integrated absorbance and concentration for the calibration range used. The new method was utilized for the analysis of shotgun pellets.